<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class=""><br class=""></div><div class="">Dear Matt,</div><div class=""><br class=""></div><div class="">Thank you for your reply.</div><div class="">We are comparing here two straightforward NVT runs (not NPT) of 64 water molecules in a box of 12.43 A. Without XC_SMOOTH_RHO, the average pressure is about zero Pa, instead with XC_SMOOTH_RHO the average pressure is about -25000 Pa. </div><div class="">A third simulation using USE_FINER_GRID gives also about zero pressure (plus or minus a thousand).</div><div class=""><br class=""></div><div class="">My guess is that there is a bug in the calculation of the XC part of the pressure tensor when using XC_SMOOTH_RHO. And it seems to me that it does not affect the forces in general, because dynamic properties such as the mean square displacement come out reasonable and only the pressure is dramatically affected. </div><div class=""><br class=""></div><div class="">best wishes,</div><div class="">Bernd</div><div class=""><br class=""></div><br class=""><div><blockquote type="cite" class=""><div class="">On 4 Dec, 2015, at 13:01 , Matt W <<a href="mailto:MattWa...@gmail.com" class="">MattWa...@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class="">Hi,<div class=""><br class=""></div><div class="">running NPT calculations are not straightforward. The stress tensor needs to be reasonably converged wrt the cutoff to get reliable results. The cutoff to converge the stress tensor might be much larger than for reliable forces.</div><div class=""><br class=""></div><div class="">Matt</div><div class=""><br class="">On Thursday, December 3, 2015 at 5:00:18 PM UTC, Bernd Ensing wrote:<blockquote class="gmail_quote" style="margin: 0;margin-left: 0.8ex;border-left: 1px #ccc solid;padding-left: 1ex;"><div dir="ltr" class=""><div class=""><br class=""></div><div class="">Dear cp2k developers,</div><div class=""><br class=""></div><div class="">Is it known whether there is a bug in the calculation of the pressure tensor when using XC_SMOOTH_RHO NN10?</div><div class="">Using this smoothing option results in very negative pressures for a typical system containing 64 water molecules (see message below of Ambuj Tiwari).</div><div class="">Does this strange behaviour also affect the forces on the atoms in general?</div><div class=""><br class=""></div><div class="">Many thanks in advance for your comments.</div><div class="">best wishes,</div><div class=""><br class=""></div><div class="">Bernd Ensing</div><div class=""><br class=""></div><br class=""><br class="">Op woensdag 25 november 2015 13:49:36 UTC+1 schreef Ambuj Tiwari:<blockquote class="gmail_quote" style="margin:0;margin-left:0.8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr" class=""><span style="font-family:verdana,sans-serif" class="">Dear All,<br class="">I am running a NVT MD simulation on bulkwater(64 water molecules) . The problem is related to pressure calculation. <br class="">I was calculating the pressure for the system and found highly negative values(in order of -25000) and then I switched all the parameters one by one and eventually found out that on changing smoothing from XC_SMOOTH_RHO NN10 to USE_FINER_GRID it came down to less negative values(-5000). Is this some kind of bug in the program or more fundamental problem.<br class=""><br class="">I am attaching the input file and bottom of .ener .stress file here.<br class=""><br class="">Regards,<br class="">Ambuj</span><br class=""><br class=""><br class=""><b class="">'input file 1'</b><br class=""> <a href="https://en.wikipedia.org/wiki/Car%E2%80%93Parrinello_molecular_dynamics#cite_note-3" rel="nofollow" target="_blank" onmousedown="this.href='https://www.google.com/url?q\75https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FCar%25E2%2580%2593Parrinello_molecular_dynamics%23cite_note-3\46sa\75D\46sntz\0751\46usg\75AFQjCNEBbQdf7Yu3wfvD3IhFcHy1--wLyw';return true;" onclick="this.href='https://www.google.com/url?q\75https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FCar%25E2%2580%2593Parrinello_molecular_dynamics%23cite_note-3\46sa\75D\46sntz\0751\46usg\75AFQjCNEBbQdf7Yu3wfvD3IhFcHy1--wLyw';return true;" class=""><span class=""></span></a><br class=""> &XC<br class=""> &XC_FUNCTIONAL BLYP<br class=""> &END XC_FUNCTIONAL<br class=""> &VDW_POTENTIAL<br class=""> DISPERSION_FUNCTIONAL PAIR_POTENTIAL<br class=""> &PAIR_POTENTIAL<br class=""> TYPE DFTD3<br class=""> PARAMETER_FILE_NAME /home/ensing/BASIS_SET/dftd3.<wbr class="">dat<br class=""> REFERENCE_FUNCTIONAL BLYP<br class=""> &END PAIR_POTENTIAL<br class=""> &END VDW_POTENTIAL<br class=""> &XC_GRID<br class=""> <b class=""> XC_SMOOTH_RHO NN10<br class=""> XC_DERIV SPLINE2_SMOOTH</b><br class=""> &END XC_GRID<br class=""> &END XC<br class=""><br class=""><b class="">'input file 2'</b><br class=""> <wbr class=""> <wbr class=""> <wbr class=""> <wbr class=""> <wbr class=""> <wbr class=""> <wbr class=""> <wbr class=""> <br class=""> &XC<br class=""> &XC_FUNCTIONAL BLYP<br class=""> &END XC_FUNCTIONAL<br class=""> &VDW_POTENTIAL<br class=""> DISPERSION_FUNCTIONAL PAIR_POTENTIAL<br class=""> &PAIR_POTENTIAL<br class=""> TYPE DFTD3<br class=""> PARAMETER_FILE_NAME /home/ensing/BASIS_SET/dftd3.<wbr class="">dat<br class=""> REFERENCE_FUNCTIONAL BLYP<br class=""> &END PAIR_POTENTIAL<br class=""> &END VDW_POTENTIAL<br class=""> &XC_GRID<br class=""><font size="2" class=""><b class=""> USE_FINER_GRID </b></font><br class=""> &END XC_GRID<br class=""> &END XC<br class=""><br class=""><div dir="ltr" class=""><br class=""><b class="">'*.ener 1'</b><br class=""> <b class=""> 163298 81649.000000 0.295424393 325.610938118 -1101.039478079 -1100.781654417 22.112000000<br class=""> 163299 81649.500000 0.294462120 324.550339188 -1101.039370784 -1100.781669902 22.078000000<br class=""> 163300 81650.000000 0.294961268 325.100490947 -1101.040473093 -1100.781725319 25.159000000<br class=""> 163301 81650.500000 0.296162908 326.424914893 -1101.042161493 -1100.781750771 22.115700000<br class=""> 163302 81651.000000 0.298814382 329.347317264 -1101.044236790 -1100.781694623 22.139200000<br class=""> 163303 81651.500000 0.301128239 331.897603891 -1101.047561646 -1100.781602129 24.739700000<br class=""> 163304 81652.000000 0.307044448 338.418332848 -1101.053434140 -1100.781587012 24.682400000<br class=""> 163305 81652.500000 0.316425516 348.757961573 -1101.061982016 -1100.781699977 22.044200000<br class=""> 163306 81653.000000 0.327014965 360.429442967 -1101.071396202 -1100.781872287 22.101900000<br class=""><br class=""><br class=""></b><br class=""><b class=""><b class="">'*.ener 2'<br class=""> 91 45.500000 0.316250053 348.564569099 -1102.663360533 -1102.332927916 65.288200000<br class=""> 92 46.000000 0.315037265 347.227857880 -1102.661696314 -1102.332913105 65.190400000<br class=""> 93 46.500000 0.314019534 346.106135819 -1102.660798344 -1102.332914267 65.276700000<br class=""> 94 47.000000 0.314010873 346.096588928 -1102.660760313 -1102.332937169 65.315200000<br class=""> 95 47.500000 0.315000947 347.187829574 -1102.661384548 -1102.332972600 65.163300000<br class=""> 96 48.000000 0.315886554 348.163928325 -1102.662099658 -1102.333054612 65.248800000<br class=""> 97 48.500000 0.315298803 347.516120600 -1102.661788013 -1102.333132240 65.120100000<br class=""> 98 49.000000 0.313543746 345.581730970 -1102.659461626 -1102.333136220 65.202000000<br class=""> 99 49.500000 0.309178417 340.770351269 -1102.655147713 -1102.333068024 63.328600000<br class=""> 100 50.000000 0.304077471 335.148189283 -1102.649908792 -1102.332978856 64.191200000<br class=""> <wbr class=""> <wbr class=""> <wbr class=""> <wbr class=""> <wbr class=""> <wbr class=""> <wbr class=""> <wbr class=""> <br class=""><br class=""></b><br class="">'*.stress 1'</b><br class=""> 163294 81647.000 -23587.6933211956 2342.2050511699 -2620.1253216644 2342.2050511699 -23228.0050606190 3414.1775796133 -2620.1253216644 3414.1775796133 -20169.0313283565<br class=""> 163295 81647.500 -22389.3419955310 1849.7028598497 -2508.5434330934 1849.7028598497 -24356.6599768539 2800.7048436858 -2508.5434330934 2800.7048436858 -22725.6161101663<br class=""> 163296 81648.000 -21214.9735696668 1148.0699336617 -2218.3871712667 1148.0699336617 -25144.9624318558 1975.3590510643 -2218.3871712667 1975.3590510643 -24795.3384458679<br class=""> 163297 81648.500 -20309.0216433928 302.8654094409 -1803.1704603762 302.8654094409 -25394.9473522949 996.8049404043 -1803.1704603762 996.8049404043 -26162.6367896449<br class=""> 163298 81649.000 -19855.8176878975 -598.7972734722 -1300.5824885129 -598.7972734722 -24999.8852946563 -79.5868061270 -1300.5824885129 -79.5868061270 -26686.2571452786<br class=""> 163299 81649.500 -19956.2226579495 -1461.2946422884 -742.0897491587 -1461.2946422884 -24019.8747323228 -1206.1348202948 -742.0897491587 -1206.1348202948 -26376.7375359960<br class=""> 163300 81650.000 -20534.1679738551 -2200.5578986806 -164.8658164621 -2200.5578986806 -22584.1267162156 -2322.5467222548 -164.8658164621 -2322.5467222548 -25268.9877352706<br class=""> 163301 81650.500 -21452.3785466678 -2746.9001879179 376.2080784084 -2746.9001879179 -20951.8376784856 -3338.3737161118 376.2080784084 -3338.3737161118 -23492.0302819538<br class=""><br class=""><br class=""><b class="">'*.stress 2'</b><br class=""> 83 41.500 14620.6789775920 1631.8725215074 2233.0775150043 1631.8725215074 6922.5364171994 1568.9298877547 2233.0775150043 1568.9298877547 4863.0813795099<br class=""> 84 42.000 13465.9504463874 1646.6798565162 1742.3968878509 1646.6798565162 7528.7642280447 1356.1689695128 1742.3968878509 1356.1689695128 3678.0979512013<br class=""> 85 42.500 11929.6829243335 1557.1878823967 1189.8285351507 1557.1878823967 7536.6702267556 906.2538614813 1189.8285351507 906.2538614813 2706.1024195638<br class=""> 86 43.000 10242.7023865733 1377.0907756499 607.2431768383 1377.0907756499 6953.6306436901 280.8453243292 607.2431768383 280.8453243292 2111.5249630222<br class=""> 87 43.500 8704.9333307887 1111.3766575987 27.5775490784 1111.3766575987 5939.0119410377 -388.5800033232 27.5775490784 -388.5800033232 2026.3208988151<br class=""> 88 44.000 7481.3245836153 770.0630298266 -494.3356330308 770.0630298266 4626.9158749281 -951.4354212867 -494.3356330308 -951.4354212867 2390.6634657579<br class=""> 89 44.500 6663.8847520724 360.1790480556 -890.4213349779 360.1790480556 3225.2634082928 -1279.9170414956 -890.4213349779 -1279.9170414956 3064.5349399335<br class=""> 90 45.000 6254.7640395386 -100.7086327357 -1091.1835737339 -100.7086327357 1954.1849838233 -1309.6032354774 -1091.1835737339 -1309.6032354774 3839.7803365830<br class=""> 91 45.500 6155.5011736691 -574.1695321638 -1051.6467240489 -574.1695321638 957.4978282879 -1053.9528084102 -1051.6467240489 -1053.9528084102 4443.4869908843<br class=""> 92 46.000 6285.5912946027 -1016.5428590808 -783.4044479712 -1016.5428590808 376.4627244754 -574.9649194818 -783.4044479712 -574.9649194818 4722.8910330993<br class=""> 93 46.500 6504.7623119346 -1380.8418795540 -361.7805767782 -1380.8418795540 216.2588001339 37.9199806709 -361.7805767782 37.9199806709 4578.5854391507<br class=""> 94 47.000 6695.7329680208 -1630.3118660115 95.8727981760 -1630.3118660115 437.0880477724 702.9749077441 95.8727981760 702.9749077441 4059.5915440691<br class=""><br class=""><br class="">Thanks in advance!<br class=""></div></div></blockquote></div></blockquote></div></div><div class=""><br class="webkit-block-placeholder"></div> -- <br class=""> You received this message because you are subscribed to the Google Groups "cp2k" group.<br class=""> To unsubscribe from this group and stop receiving emails from it, send an email to <a href="mailto:cp2k+uns...@googlegroups.com" class="">cp2k+uns...@googlegroups.com</a>.<br class=""> To post to this group, send email to <a href="mailto:cp...@googlegroups.com" class="">cp...@googlegroups.com</a>.<br class=""> Visit this group at <a href="http://groups.google.com/group/cp2k" class="">http://groups.google.com/group/cp2k</a>.<br class=""> For more options, visit <a href="https://groups.google.com/d/optout" class="">https://groups.google.com/d/optout</a>.<br class=""> </div></blockquote></div><br class=""></body></html>